Large memory systems may service a plurality of individual using applications or clients, and such applications or clients may operate independently of each other as in, for example, virtualized systems. Alternatively, a plurality of applications may access and operate on a common memory area, such as where data has been de-duplicated, and is accessed by a plurality of users or were read-only access is provided to a plurality of users. The memory system may thus be partitioned, for example, into private (exclusive) memory areas or into shared memory areas, or any combination or variation thereof, a memory location, or range thereof, being subject to configurable access criteria. Depending on the specific needs of an application, the memory areas may be configured so as to have different reliability, access time, bandwidth and other characteristics. These characteristics may be expressed, for example, as a selection of the RAID type to be employed, the striping of the data (wide or narrow, for example), or other selectable system attributes, such as the bandwidth of the port through which a server accesses the memory system, the memory extent allocated, data backup provisions and access permissions. These attributes may be embodied in hardware, or configurable by an algorithm, data table, or the like.
A memory area may be allocated to a particular application or client may be described as a Logical Unit, and each Logical Unit may be designated, for example by a number N: hence, LUN.
As the address space size of a memory system grows, the number or bandwidth of the access points thereto may need to increase, and consideration take account of the impact of read and write loading on the access time (latency), on load balancing between the various entities (e.g., servers), and on coordinating the access to a memory location that is shared by a plurality of users. Further, in any large electronic system, hardware failures occur, and an attribute of such systems may be to isolate a failure so as to affect the smallest number of users, or to permit the repair of the failure, including recovery of the associated data, while maintaining operation of the memory system, or a portion thereof.